Open 3 Windows. Separate it into 3 different spaces. Finalize the Vivaldi or restart the Mac.
Reopen Vivaldi - all open right as before, but at the same space 0 (The current one).
The ideal would be re-open all three Windows in the spaces as I determined. Thus improving productivity. And avoiding the stress of having to rearrange everything whenever you need to restart the MAC or even when there is a crash.